Computing devices, such as notebook computers, personal data assistants (PDAs), and mobile handsets, have user interface devices, which are also known as human interface device (HID). One user interface device that has become more common is a touch-sensor pad. A basic notebook touch-sensor pad emulates the function of a personal computer (PC) mouse. A touch-sensor pad is typically embedded into a PC notebook for built-in portability. A touch-sensor pad replicates mouse x/y movement by using two defined axes which contain a collection of sensor elements that detect the position of a conductive object, such as a finger. Mouse right/left button clicks can be replicated by two mechanical buttons, located in the vicinity of the touchpad, or by tapping commands on the touch-sensor pad itself. The touch-sensor pad provides a user interface device for performing such functions as positioning a cursor, or selecting an item on a display. These touch-sensor pads may include multi-dimensional sensor arrays for detecting movement in multiple axes. The sensor array may include a one-dimensional sensor array, detecting movement in one axis. The sensor array may also be two dimensional, detecting movements in two axes.
FIG. 1A illustrates a conventional touch-sensor pad. The touch-sensor pad 100 includes a sensing surface 101 on which a conductive object may be used to position a cursor in the x- and y-axes, or to select an item on a display. Touch-sensor pad 100 may also include two buttons, left and right buttons 102 and 103, respectively. These buttons are typically mechanical buttons, and operate much like a left and right button on a mouse. These buttons permit a user to select items on a display or send other commands to the computing device.
FIG. 1B illustrates a conventional linear touch-sensor slider. The linear touch-sensor slider 110 includes a surface area 111 on which a conductive object may be used to position a cursor in the x-axes (or alternatively in the y-axes). The construct of touch-sensor slider 110 may be the same as that of touch-sensor pad 100. Touch-sensor slider 110 may include a one-dimensional sensor array. The slider structure may include one or more sensor elements that may be conductive traces. Each trace may be connected between a conductive line and a ground. By being in contact or in proximity on a particular portion of the slider structure, the capacitance between the conductive lines and ground varies and can be detected. The capacitance variation may be sent as a signal on the conductive line to a processing device. For example, by detecting the capacitance variation of each sensor element, the position of the changing capacitance can be pinpointed. In other words, it can be determined which sensor element has detected the presence of the conductive object, and it can also be determined the motion and/or the position of the conductive object over multiple sensor elements.
One difference between touch-sensor sliders and touch-sensor pads may be how the signals are processed after detecting the conductive objects. Another difference is that the touch-sensor slider is not necessarily used to convey absolute positional information of a conducting object (e.g., to emulate a mouse in controlling cursor positioning on a display) but, rather, may be used to actuate one or more functions associated with the sensing elements of the sensing device.
FIG. 1C illustrates a top-side view of a conventional two-dimensional sensor array 120 of touch-sensor pad 100. In this conventional design the sensor elements are squares, configured in a grid-like pattern. The square sensor elements are coupled together in rows and columns. Alternating columns correspond to x- and y-axis sensor elements. This conventional sensor array 120 includes three rows 104(1)-104(3) (illustrated as hashed squares) and three columns 105(1)-105(3) of sensor elements (illustrated as solid squares). The sensor elements of the rows and columns are coupled together by interconnects 106 and 107, respectively. Interconnects 106 and 107 may be on the same or different layers as the sensor elements. Each sensor element includes a solid surface area of conductive material. The touch-sensor pad layout grid-like pattern may be used to maximize the surface area covered by conductive material (e.g., copper), in relation to spaces necessary to define the rows and columns. Typically, each column and row is coupled to a single pin of a processing device.
FIG. 1D illustrates a top-side view of a conventional one-dimensional sensor array 130 of touch-sensor slider 110. In this conventional design the sensor elements are solid rectangular bars having two slanted sections. Each solid rectangular bar is a single column. This conventional sensor array 130 includes nine columns 151(1)-151(9) of sensor elements (illustrated as solid rectangular bars). Each sensor element includes a solid surface area of conductive material. The touch-sensor slider layout pattern may be used to maximize the surface area covered by conductive material (e.g., copper), in relation to spaces necessary to define the columns. Typically, one column (e.g., one sensor element) is coupled to a single pin of a processing device.
In touch-sensor pads and sliders, the surface area of the conductive material of each row and/or column is proportional to the charge time and charge current that is used in measuring the capacitance on each sensor element.